Search Results

This chapter explores the role of mesolimbic dopamine projection in translating motivation into action in the brain. First, it describes the anatomy and physiology of mesolimbic dopamine and then investigates why it is implicated in motivating actions and the control of behavior. Finally, the chapter considers the limitations of the mesolimbic dopamine system in translating motivation into action.

Chapter 5 reviews the brain circuits that regulate maternal behavior in nonhuman mammals. The medial preoptic area (MPOA) is essential for both the onset and maintenance of maternal behavior. Hormones and oxytocin act on the MPOA to stimulate the onset of maternal behavior. The neurotransmitters contained within MPOA neurons that may regulate maternal behavior are described, as are several neural inputs to the MPOA that regulate its output. A defensive neural circuit that inhibits maternal behavior in most virgin female mammals is described. MPOA output stimulates maternal behavior by depressing the defensive circuit while also activating neural circuits that underpin maternal motivation. MPOA output to the mesolimbic dopamine system is essential for appetitive maternal responses, while its output to the periaqueductal gray regulates consummatory responses. Synaptic plasticity within the MPOA-to-mesolimbic DA circuit is involved in the development of an enduring mother–infant bond.

This chapter offers an explicit description of the assumptions of medical models, the different forms they may take, and the challenges they face in providing explanations with solid evidence of addiction. Medical models of addiction imply that there are in principle clear criteria for the differential diagnosis of addiction. The chapter shows that the predominant working medical model of addiction based on the mesolimbic dopamine system spans multiple levels from molecules to behavior, and highlights the role of social factors in onset, current addiction, remission, and relapse. In general, it illustrates that the medical models of addiction are bold, interesting, and parsimonious accounts, and have directed a research program which has produced many important results.

Chapter 8 reviews the human parental brain. Most functional magnetic resonance imaging research has examined the maternal brain, with some research on the paternal brain. Although woman show allomaternal behavior, defensive neural circuits may depress maternal responsiveness under certain conditions. The subcortical circuits associated with human maternal behavior match those in nonhuman mammals and include medial preoptic area, mesolimbic dopamine, amygdala, and oxytocin neural systems. Interacting with these subcortical circuits are cortical regions, including dorsomedial prefrontal cortex and anterior insula, that are involved in maternal cognitions, empathy, emotions, and emotion regulation. The medial prefrontal cortex connects some of these cortical regions with the subcortical circuitry so that maternal cognitions and emotions can be translated into appropriate maternal behavior. The poor maternal behavior associated with postpartum depression may result from dysfunctions within these circuits, and alterations in corticotropin-releasing factor and OT may be involved.

Chapter 10 deals with the development of the parental brain in humans, emphasizing experiential influences on the intergenerational continuity of maternal behavior: A history of experiencing childhood maltreatment (CMT; maternal neglect and/or abuse) is associated with alterations in the development of the child’s parental brain, which may lead to subsequent deficits in its maternal behavior. The manner in which parents treat their children may affect the development of neural systems (a) that regulate emotionality, with poor parental care resulting in deficits in emotion regulation, and (b) that underpin maternal motivation, love, and empathy, with poor parental care decreasing these processes. Alterations in the development of medial prefrontal cortex, amygdala, mesolimbic dopamine, oxytocin, corticotropin-releasing factor, and serotonin neural systems are involved, as are epigenetic effects. Not all mothers who experience CMT become poor mothers, and the involvement of gene by environment interactions are highlighted.

Chapter 9 examines the development of the parental brain in animals, emphasizing that the way a mother treats her offspring affects their brain development and their subsequent maternal behavior, leading to an intergenerational continuity of maternal phenotypes. Two proposals are evaluated. First, maternal treatment influences the development of maternal motivation circuits in offspring. In support, the development of medial preoptic area projections to the mesolimbic dopamine system is affected. Second, maternal treatment influences the development of neural systems that regulate anxiety and stress reactivity in offspring. In support, the development of medial prefrontal cortex regulation of amygdala reactivity to stressful situations is affected. Deficient development of maternal motivation circuits may contribute to neglectful maternal behavior; deficient development of emotion regulation circuits may contribute to abusive maternal behavior. Epigenetics, particularly DNA methylation, and gene by environment interactions are involved in these processes.